1. Field of the Invention
The present invention broadly relates to compact pulse-firing pocket engine assemblies. More particularly, the invention relates to such an engine which utilizes a pair of cross-linked parallel piston valves. The present invention is particularly adapted for spin stabilization and guidance of small vehicles.
2. Description of the Prior Art
Both liquid and solid fuel rocket engines have been known for many years. The liquid or fluid fueled rocket engines have provided the primary propulsion systems for virtually all of the world's exploration of space. Indeed, in most programs which requires high performance and low weight, the liquid or fluid fueled rockets have been preferred over the solid rockets. A particular advantage of liquid rockets is that they may be started and stopped substantially as desired whereas solid rockets are traditionally "one-shot" devices. A disadvantage of the liquid rockets, however, is that they are inherently more complex than solid rockets. The complexity of the liquid rockets is a result of the requirements for some means of providing propellants at pressure such as by pressurization of the storage tanks, a positive expulsion mechanism, pumps or the like. In addition, the liquid fueled rockets require sophisticated valves and elaborate plumbing for delivery of the fuel and regulation of its flow. Obviously, these factors add to the weight and bulk of the liquid rocket propulsion systems.
In addition to the main propulsion engines which are used to launch vehicles, there is a need for smaller reaction or rocket engines which are capable of intermittent firing for vehicle attitude adjustment, course changes, stabilization and the like. An example of a valve for such applications, is described in U.S. Pat. No. 3,479,818. The patent discloses an apparatus and method for feeding pulsating fluid propellant rocket engines. The method utilizes an energy-operated pump and an elastic storing member such as a spring. The method comprises storing pump operating energy by using the operating pressure of the rocket engine during each high pressure phase of operation and utilizing the stored energy during the low pressure phase of operation to drive the energy-operated pump and to direct the propellant into the combustion chamber so that the cycle is repeated. A disadvantage of this apparatus and method is that it utilizes a spring-operated pump device which is not only heavy, but lacks a rapid pulse response time. Further, the apparatus chamber pressure is limited by the spring utlized.
More recently, there has been suggested in U.S. Pat. No. 4,258,546 a rocket propulsion system which utilizes vehicles' spin forces to charge a specific amount of propellant through a differential area piston to create high chamber pressure. A disadvantage of this system, however, is that it utilizes a plurality of valves adding to its weight and complexity and more importantly, is not amenable to scaling down to small sizes. Accordingly, there exists a need for a small, compact engine suitable for use with, for example, a so-called kinetic energy weapon. Typically such weapons will require no more than 10 to 20 pounds of thrust for pulse durations of a few milliseconds to provide the desired spin stabilization, course correction, or both.